## Search found 28 matches

Sun Jun 03, 2018 11:06 pm
Forum: Hybridization
Topic: Sigma Bonds
Replies: 5
Views: 297

### Re: Sigma Bonds

Also, sigma bonds are those formed between orbitals end-to-end, so they allow bound atoms to rotate, unlike pi bonds.
Sun Jun 03, 2018 11:04 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: AXE formula
Replies: 32
Views: 4686

### Re: AXE formula

Yes. A represents the center atom, X represents atoms bonded to the center atom, and E represents lone electron pairs. X and E together represent regions of electron density.
Each AXE formula corresponds to a different molecular structure shown in the chart posted by Jack.
Sun Jun 03, 2018 10:58 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi bonds
Replies: 3
Views: 312

### Re: Sigma and Pi bonds

We would likely be given a bond (single, double, or triple) and be asked to find the number of sigma/pi bonds. We should also be able to identify the fact that sigma bonds are two orbitals bonding end-to-end where bond atoms can rotate, whereas pi bonds are two orbitals bonding side-by-side where bo...
Thu May 24, 2018 9:59 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charge with ions
Replies: 4
Views: 350

### Re: Formal charge with ions

The last answer explains it well. The charge of the ion should be the same as the formal charge. This is why the formal charges of atoms and molecules should be equal to 0 if they are not ionized.
Thu May 17, 2018 7:50 pm
Forum: Lewis Structures
Replies: 2
Views: 173

I don't see any way for that to happen because each orbital can only contain two electrons, and by definition, a radical is an atom, molecule, or ion with an unpaired valence electron.
Thu May 17, 2018 7:42 pm
Forum: Lewis Structures
Topic: HW 3.41 part c)
Replies: 1
Views: 124

### Re: HW 3.41 part c)

Yes, a lot of complex organic molecules are structured like this. This is because organic molecules may contain certain "functional groups" that give the molecules specific properties. For example, COOH is a carboxyl group and NH2 is an amino group. Writing the groups separately in the che...
Thu May 17, 2018 7:35 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 3
Views: 302

### Re: Formal Charge

Yes, correct.
Sun May 13, 2018 12:12 am
Forum: Formal Charge and Oxidation Numbers
Topic: Oxidation Number & Bonds
Replies: 6
Views: 312

### Re: Oxidation Number & Bonds

Cl will basically always become Cl- (oxidation number -1) to achieve a full octet. Gaining one electron is much easier than losing 7 electrons. Some other elements, however, have almost equally likely oxidation states. One example is Cu, which can become Cu+ (oxidation number +1) or Cu2+ (oxidation ...
Sun May 13, 2018 12:07 am
Forum: Ionic & Covalent Bonds
Replies: 9
Views: 520

These atoms or molecules are found whenever the number of valence electrons is odd, leaving one unpaired valence electron.
Fri May 11, 2018 3:05 pm
Forum: Lewis Structures
Topic: Ionic vs Covalent
Replies: 5
Views: 340

### Re: Ionic vs Covalent

Usually, ionic bonds are between metals and non-metals, whereas covalent bonds are between non-metals and other non-metals.
Sun May 06, 2018 2:03 pm
Forum: Trends in The Periodic Table
Replies: 4
Views: 304

As you go across a period, there are more protons as well as electrons and unlike going down in a group, all the electrons are in the same shell. When more protons and more electrons are added (electrons to the same shell), the attraction is greater and the electrons are pulled in, decreasing atomic...
Sun May 06, 2018 1:59 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: HW 2.29 [ENDORSED]
Replies: 4
Views: 312

### Re: HW 2.29[ENDORSED]

The Pauli Exclusion Principle states that no two electrons in an atom can have the same four quantum numbers. Since in b) and d), ml is given, we know there can only be two electrons described by these numbers (one with ms=+1/2 and one with ms=-1/2). So the value of ml doesn't actually matter. It's ...
Fri May 04, 2018 2:01 pm
Forum: Trends in The Periodic Table
Topic: Issues with 7th Edition Textbook
Replies: 3
Views: 205

### Re: Issues with 7th Edition Textbook

Thanks so much! It's patienceolsen@gmail.com
Fri May 04, 2018 2:02 am
Forum: Trends in The Periodic Table
Topic: Ionization Energy
Replies: 4
Views: 268

### Re: Ionization Energy

Ionization energy refers to the energy required to remove an electron from an atom while electron affinity refers to the energy released when an electron is added to an atom. The trends for both correlate. For example, a halogen element (group 17) is very likely to gain an electron, so it will have ...
Thu May 03, 2018 11:19 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Question 1.19 Help
Replies: 2
Views: 163

### Re: Question 1.19 Help

You can also use the formula for the number of electrons that can occupy a subshell: ml=2l+1
For (b), you would plug in l=2 to get ml=5 and for (c), you would plug in l=1 to get ml=3.
Thu May 03, 2018 11:08 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy
Replies: 4
Views: 268

### Re: Ionization Energy

Yes, lower is just meant to be a relative term and doesn't correspond to a specific value. An element with a lower IE is more likely to become a cation than an element with a higher IE because it doesn't take as much energy to remove an electron from the element with lower IE.
Thu May 03, 2018 11:00 pm
Forum: Trends in The Periodic Table
Topic: Issues with 7th Edition Textbook
Replies: 3
Views: 205

### Issues with 7th Edition Textbook

I made a terrible mistake by purchasing the 7th edition textbook because the questions in this textbook do not align with the questions in the 6th edition textbook, even though it says on the Chem 14A website that the 7th edition textbook is fine to use. For Fundamentals and Chapter 1, I was able to...
Thu May 03, 2018 10:29 pm
Forum: Properties of Electrons
Topic: Electron Affinity
Replies: 4
Views: 394

### Re: Electron Affinity

Electron affinity is the amount of energy released when an electron is added to a neutral atom. It can also be understood as the likelihood of an atom to accept an electron, so the halogens have the greatest electron affinity of all elements. Noble gases, being in a stable state, have the lowest ele...
Thu May 03, 2018 8:12 pm
Forum: Ionic & Covalent Bonds
Topic: Octet
Replies: 7
Views: 498

### Re: Octet

Also, the eight electrons come from two electrons in the s-orbital and six electrons in the p-orbital for most atoms. Hope this clarifies things a bit.
Fri Apr 20, 2018 10:41 am
Forum: Photoelectric Effect
Topic: Lyman vs. Balmer vs. Paschen vs. Brackett?
Replies: 3
Views: 467

### Re: Lyman vs. Balmer vs. Paschen vs. Brackett?

The last comment is correct. Series are defined by the amount of energy they contain, and wavelengths in the Lyman series, for example, are grouped together because the light has enough energy to reduce an electron to its ground state (n=1). The Lyman series represents the UV spectrum, Balmer repres...
Thu Apr 19, 2018 11:37 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Lyman and Balmer Series
Replies: 3
Views: 224

### Re: Lyman and Balmer Series

To add on to previous answers, the Lyman series represents the highest energy series (UV), with enough energy to reduce electrons to the lowest energy level n=1. The Balmer series represents the second highest energy series (visible light), with enough energy to reduce electrons to the energy level ...
Thu Apr 19, 2018 10:06 pm
Forum: General Science Questions
Topic: Notation
Replies: 3
Views: 438

### Re: Notation

I don't think there should be any special reason for this difference. Either way, the difference doesn't concern us because it wouldn't affect our marks.
Wed Apr 11, 2018 1:43 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Parent acids
Replies: 1
Views: 250

### Re: Parent acids

By the Arrhenius theory, an acid is any compound that releases a hydrogen ion into solution when dissolved. There are other acids (Brønsted–Lowry and Lewis) that go beyond this theory but that's irrelevant to the question. Basically, the release of a hydrogen ion in solution is one way to define a c...
Wed Apr 11, 2018 1:27 pm
Forum: Molarity, Solutions, Dilutions
Topic: Homework problem G13
Replies: 1
Views: 155

### Re: Homework problem G13

Refer to the answer for https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=10&t=30583 . The first step is to find the molarity of the diluted solution. The person asking the question above solved this by using the dilution formula M1V1 = M2V2. This formula is based on the fact that the number o...
Wed Apr 11, 2018 1:07 pm
Forum: Molarity, Solutions, Dilutions
Topic: Fundamentals HW G.13
Replies: 1
Views: 211

### Re: Fundamentals HW G.13

Find the moles of NH4NO3 in each 100. mL sample:
0.050 mol NH4NO3/L * 0.100 L = 0.0050 mol NH4NO3

In each molecule of NH4NO3, there are 2 nitrogen atoms. Multiply by this ratio to find the moles of nitrogen:
0.0050 mol NH4NO3 * 2 mol N/1 mol NH4NO3 = 0.0100 mol N

Each plant receives 0.0100 mol N.
Tue Apr 10, 2018 11:39 pm
Forum: Properties of Electrons
Topic: Electromagnetic Field [ENDORSED]
Replies: 7
Views: 425

### Re: Electromagnetic Field[ENDORSED]

Anyone please correct me if I'm wrong but I think it's arbitrary which field points in which direction, and it's only done this way for convention. What matters is that the waves propagate at right angles to one another.
Tue Apr 10, 2018 11:29 pm
Forum: Molarity, Solutions, Dilutions
Topic: Outline 1 (Molarity,solutions, Dilutions) #25
Replies: 2
Views: 169

### Re: Outline 1 (Molarity,solutions, Dilutions) #25

Find molarity (M) of the original solution: 5.00 g KMnO4/0.15000 L soln * 1 mol KMnO4/158.04 g KMnO4 = 0.211 mol/L = 0.211 M Find how many moles of KMnO4 are present in 20.00 mL of this solution using molarity from previous step: 0.211 mol/L * 0.02000 L = 0.00422 mol KMnO4 Find molarity of the new s...
Tue Apr 10, 2018 11:09 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Formula Units
Replies: 6
Views: 8754

### Re: Formula Units

Formula units are basically empirical formulas for ionic compounds, but in most questions just represent molecules (in their simplest, empirical form). For example, E.9 (b) asks for the number of formula units of magnesium sulfate heptahydrate in a 5.15 g sample of the compound. This question is sol...